Recent years have witnessed practical use of a flat-panel display in various products and fields. This has led to a demand for a flat-panel display that is larger in size, achieves higher image quality, and consumes less power.
Under such circumstances, great attention has been drawn to an organic EL display device that (i) includes an organic electroluminescence (hereinafter abbreviated to “EL”) element which uses EL of an organic material and that (ii) is an all-solid-state flat-panel display which is excellent in, for example, low-voltage driving, high-speed response, self-emitting.
An organic EL display device includes, for example, (i) a substrate made up of members such as a glass substrate and TFTs (thin film transistors) provided to the glass substrate and (ii) organic EL elements provided on the substrate and connected to the TFTs.
An organic EL element is a light-emitting element capable of high-luminance light emission based on low-voltage direct-current driving, and includes in its structure a first electrode, an organic EL layer, and a second electrode stacked on top of one another in that order, the first electrode being connected to a TFT. The organic EL layer between the first electrode and the second electrode is an organic layer including a stack of layers such as a hole injection layer, a hole transfer layer, an electron blocking layer, a luminescent layer, a hole blocking layer, an electron transfer layer, and an electron injection layer.
For example, a full-color organic EL display device typically includes, as sub-pixels aligned on a substrate, organic EL elements including luminescent layers of red (R), green (G), and blue (B). The full-color organic EL display device carries out a color image display by, with use of TFTs, selectively causing the organic EL elements to each emit light with a desired luminance.
In order to produce an organic EL display device, it is therefore necessary to form, for each organic EL element, a luminescent layer of a predetermined pattern made of an organic luminescent material which emits light of the colors. A layer that is not required to be patterned in shapes for respective organic EL elements is formed collectively in an entire pixel region constituted by the organic EL elements.
Such formation of a luminescent layer of a predetermined pattern is performed by a method such as (i) a vacuum vapor deposition method, (ii) an inkjet method, and (iii) a laser transfer method. The production of, for example, a low-molecular organic EL display (OLED) often uses a vacuum vapor deposition method (e.g. Patent Literatures 1 and 2).
The vacuum vapor deposition method uses a mask (also called a vapor deposition mask or a shadow mask) provided with openings of a predetermined pattern. The mask is fixed in close contact with a vapor-deposited surface of a substrate which vapor-deposited surface faces a vapor deposition source. Then, vapor deposition particles (film formation material) are injected from the vapor deposition source so as to be deposited on the vapor-deposited surface through openings of the mask. This forms a thin film of a predetermined pattern. The vapor deposition is carried out for each color of a luminescent layer. This is called “selective vapor deposition”.
The following will discuss, with reference to FIGS. 13 and 14, a configuration of a conventional vapor deposition device which employs a vacuum deposition method.
FIG. 13 is a side view schematically illustrating a configuration of a conventional vapor deposition device 250. FIG. 14 is a perspective view schematically illustrating a configuration of a vapor deposition source unit 290 of the vapor deposition device 250.
As shown in FIG. 13, the vapor deposition device 250 is a device to be placed in a vacuum chamber and to form a film on a film formation substrate 260. The vapor deposition device 250 includes a shadow mask 280 and a vapor deposition source unit 290. The vapor deposition source unit 290 includes a vapor deposition source 291 and a vapor deposition source crucible 293, which are secured to a support (not illustrated).
The vapor deposition source 291 has a plurality of injection holes (nozzles) 292 from which vapor deposition particles are injected. The injection holes 292 are arranged in a line as shown in FIG. 14.
The vapor deposition source crucible 293 contains a vapor deposition material which is in solid or liquid form. The vapor deposition material is heated in the vapor deposition source crucible 293 so as to be gaseous vapor deposition particles and supplied (introduced) via a pipe 294 to the vapor deposition source 291. The pipe 294 is connected to the vapor deposition source 291 at an end (supply-side end) where one end of the line of the injection holes 292 is located. The vapor deposition particles thus supplied to the vapor deposition source 291 are injected from the injection holes 292. Note that the pipe 294 is heated to such a temperature that the vapor deposition particles do not adhere to the pipe 294.
The film formation substrate 260 and the vapor deposition source 291 are arranged such that a vapor-deposited surface of the film formation substrate 260 faces the vapor deposition source 291. The shadow mask 280, which has an opening corresponding to a pattern of a vapor deposition region, is attached tightly to the vapor deposited-surface of the film formation substrate 260 so that no vapor deposition particles adhere to a region other than the intended vapor deposition region.
According to the configuration, while the vapor deposition particles are injected from the injection holes 292, the film formation substrate 260 and the shadow mask 280 are moved (scanned) relative to the vapor deposition source 291. This forms a predetermined pattern on the film formation substrate 260.